The Gram-negative bacterium Campylobacter is the most common bacterial cause of human gastroenteritis in North America and many industrialized countries. Campylobacter is also a significant foodborne pathogen in livestock, including poultry, which are considered to be a major source of human campylobacteriosis. Thus, on-farm control of Campylobacter in poultry would reduce the risk of human exposure to this pathogen and have a significant impact on food safety and public health.
Campylobacter is endemic to many developing countries, mainly owing to poor sanitary conditions and close human contact with animals that are the reservoirs of the pathogen. A report by Katarzyna et al. Expert Rev. Vaccines 8: 625-645, 2009), suggests that in the United States, Campylobacter infections are the cause of 1.5 million (World Health Organization data) to 2.4 million (U.S. Centers for Disease Control data) disease cases each year. In addition, according to the World Health Organization, approximately 1% of the Western European population is annually infected by Campylobacter spp. Human infections are caused mainly by two species: C. coli and C. jejuni, which are responsible for over 95% of campylobacteriosis cases. Clinical manifestations of Campylobacter infections can range from asymptomatic cases to severe gastroenteritis, accompanied by sometimes long-lasting mucous, bloody, or watery diarrhea.
The publication of Jun Lin “Novel Approaches for Campylobacter Control in Poultry” (FOODBORNE PATHOGENS AND DISEASE, Volume 6, Number 7, pp. 755-765, 2009), incorporated herein by reference, discusses various strategies for reducing Campylobacter infection in poultry. Lin suggests three general strategies to control Campylobacter in poultry at the farm level: (1) reduction of environmental exposure (biosecurity measures), (2) an increase in poultry's host resistance to reduce Campylobacter carriage in the gut (e.g., competitive exclusion, vaccination, and host genetics selection), and (3) the use of antimicrobial alternatives to reduce and even eliminate Campylobacter from colonized chickens (e.g., bacteriophage therapy and bacteriocin treatment). Lin further states that except for biosecurity measures, the other intervention approaches are not commercially available and are still under development.
Elimination of these pathogens from livestock can serve as a means to reduce the incidence of infection in humans and prevent spread in farms animals. Vaccination on farms can also reduce the risk of human contamination from eating or handling animal products as well as contamination by fecal shedding of bacteria from livestock manure. Treatment of campylobacteriosis with antibiotics is also becoming increasingly challenging as antibiotic resistance of Campylobacter to previously effective antibiotics is becoming more common.
Glycosylation had once been considered to be specifically a eukaryotic phenomenon but was later shown to be widespread in both the Archaeal and Bacterial domains. Bacterial O- and N-linkages are formed with a wider range of sugars than those observed in eukaryotic glycoproteins. A general glycosylation pathway for proteins in Bacteria was first demonstrated in C. jejuni. (Szymanski et al. Molecular Microbiology 32: 1022-1030, 1999). The glycosylation machinery of C. jejuni has been characterized and has even been successfully transferred to E. coli (Wacker et al. Science, 298: 1790-1793, 2002) and active N-glycosylation of proteins was demonstrated (Young et al. J Biol Chem, 277: 42530-42539, 2002; Wacker et al. Science, 298: 1790-1793, 2002). The gene locus of C. jejuni, termed pgl (for protein glycosylation), is involved in the glycosylation of multiple proteins. Its mutational silencing results in loss of immunogenicity in multiple proteins, among many biological phenotypes.
U.S. Patent Application Publication 2006/0165728 A1, now U.S. Pat. No. 7,598,354, incorporated herein by reference, identifies a specific and highly immunogenic heptasaccharide that is present in a plurality of periplasmic and surface-exposed glycoproteins of C. jejuni. This heptasaccharide is common to at least several Campylobacter species and numerous strains that are important as human and veterinary pathogens (Nothaft et al. Mol. Cell. Proteomics 11: 1203-1219, 2012). The heptasaccharide has the following formula (I): GalNAc-α1,4-GalNAc-α1,4-[Glc-β-1,3]GalNAc-α1,4-GalNAc-α1,4-GalNAc-α1,3-diNAcBac, wherein diNAcBac (also termed di-N-acetylbacillosamine) is 2,4-diacetamido-2,4,6-trideoxy-D-glucopyranose, GalNAc is N-acetyl-galactosamine and Glc is glucose. This glycan moiety is a component of multiple glycoproteins. In C. jejuni the N-glycan is important for the interaction of C. jejuni with host cells. Mutations in the glycosylation machinery lead to decreased colonisation of intestinal tracts in mice and chickens. In C. jejuni the N-glycan is important for attachment and invasion of human epithelial cells (Szymanski et al. Infect Immun 70: 2242-2244, 2002), colonization of the intestinal tracts of mice and chickens (Kelly et al. J Bacteriol 188: 2427-2434, 2006; Szymanski et al. Infect Immun 70: 2242-2244, 2002; Hendrixson & DiRita, Mol Microbiol 52: 471-484, 2004; Karlyshev et al. Microbiology 150: 1957-1964, 2004), natural competence in strains with Type IV secretion systems (Larsen et al. J Bacteriol 186: 6508-6514, 2004) and for binding to the human macrophage C-type lectin, MGL (van Sorge et al, Cell Microbiol 11: 1768-1781, 2009). Moreover, Campylobacter surface N-glycans were shown to play protective roles against chicken gut proteases resulting in increased bacterial fitness (Alemka et al. Infect Immun 81: 1674-82, 2013).
U.S. Pat. No. 9,309,493 describes a Salmonella enterica strain comprising at least one pgl operon of C. jejuni or a functional derivative thereof and presenting at least one N-glycan of C. jejuni, or glycan derivative thereof, on its cell surface. This recombinant S. enterica is hypothesized to be useful in a vaccine against Campylobacter infections, particularly in livestock, such as poultry. However, unfortunately, subsequent publications have shown that while the recombinant S. enterica expressing the N-glycan from Campylobacter on its surface was able to colonize chickens without causing disease, there was no detectable humoral immune response in the vaccinated chickens against the Campylobacter N-glycan (Thommen “Campylobacter N-glycan presenting Salmonella Typhimurium: a new vaccine for broiler chickens?” Zurich Open Repository and Archive, University of Zurich, Dissertation, Vetsuisse Faculty, 2011). Furthermore, there was no reduction in colonization of C. jejuni in the vaccinated chickens upon infection with a C. jejuni challenge.
There remains a need for an effective vaccine for preventing and/or treating Campylobacter infections in humans and animals, in particular livestock, more particularly poultry.
This background information is provided for the purpose of making known information believed by the applicant to be of possible relevance to the present invention. No admission is necessarily intended, nor should be construed, that any of the preceding information constitutes prior art against the present invention.